/*
 *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef COMMON_VIDEO_H265_H265_COMMON_H_
#define COMMON_VIDEO_H265_H265_COMMON_H_

#include <memory>
#include <vector>

#include "rtc_base/buffer.h"

namespace webrtc {

    namespace H265 {
        // The size of a full NALU start sequence {0 0 0 1}, used for the first NALU
        // of an access unit, and for SPS and PPS blocks.
        const size_t kNaluLongStartSequenceSize = 4;

        // The size of a shortened NALU start sequence {0 0 1}, that may be used if
        // not the first NALU of an access unit or an SPS or PPS block.
        const size_t kNaluShortStartSequenceSize = 3;

        // The size of the NALU type byte (2).
        const size_t kNaluTypeSize = 2;

        enum NaluType : uint8_t {
            kTrailN = 0,
            kTrailR = 1,
            kTsaN = 2,
            kTsaR = 3,
            kStsaN = 4,
            kStsaR = 5,
            kRadlN = 6,
            kRadlR = 7,
            kBlaWLp = 16,
            kBlaWRadl = 17,
            kBlaNLp = 18,
            kIdrWRadl = 19,
            kIdrNLp = 20,
            kCra = 21,
            kRsvIrapVcl23 = 23,
            kVps = 32,
            kSps = 33,
            kPps = 34,
            kAud = 35,
            kPrefixSei = 39,
            kSuffixSei = 40,
            kAP = 48,
            kFU = 49
        };

        enum SliceType : uint8_t { kB = 0, kP = 1, kI = 2 };

        struct NaluIndex {
            // Start index of NALU, including start sequence.
            size_t start_offset;
            // Start index of NALU payload, typically type header.
            size_t payload_start_offset;
            // Length of NALU payload, in bytes, counting from payload_start_offset.
            size_t payload_size;
        };

        // Returns a vector of the NALU indices in the given buffer.
        std::vector<NaluIndex> FindNaluIndices(const uint8_t* buffer,
            size_t buffer_size);

        // Get the NAL type from the header byte immediately following start sequence.
        NaluType ParseNaluType(uint8_t data);

        // Methods for parsing and writing RBSP. See section 7.4.2 of the H265 spec.
        //
        // The following sequences are illegal, and need to be escaped when encoding:
        // 00 00 00 -> 00 00 03 00
        // 00 00 01 -> 00 00 03 01
        // 00 00 02 -> 00 00 03 02
        // And things in the source that look like the emulation byte pattern (00 00 03)
        // need to have an extra emulation byte added, so it's removed when decoding:
        // 00 00 03 -> 00 00 03 03
        //
        // Decoding is simply a matter of finding any 00 00 03 sequence and removing
        // the 03 emulation byte.

        // Parse the given data and remove any emulation byte escaping.
        std::vector<uint8_t> ParseRbsp(const uint8_t* data, size_t length);

        // Write the given data to the destination buffer, inserting and emulation
        // bytes in order to escape any data the could be interpreted as a start
        // sequence.
        void WriteRbsp(const uint8_t* bytes, size_t length, rtc::Buffer* destination);

        uint32_t Log2(uint32_t value);
    }  // namespace H265
}  // namespace webrtc

#endif  // COMMON_VIDEO_H265_H265_COMMON_H